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Disclaimer

Although the information contained in this Code has been obtained from sources believed to be reliable, New Zealand Metal Roofing Manufacturers Inc. makes no warranties or representations of any kind (express or implied) regarding the accuracy, adequacy, currency or completeness of the information, or that it is suitable for the intended use.

Compliance with this Code does not guarantee immunity from breach of any statutory requirements, the New Zealand Building Code or relevant Standards. The final responsibility for the correct design and specification rests with the designer and for its satisfactory execution with the contractor.

While most data have been compiled from case histories, trade experience and testing, small changes in the environment can produce marked differences in performance. The decision to use a particular material, and in what manner, is made at your own risk. The use of a particular material and method may, therefore, need to be modified to its intended end use and environment.

New Zealand Metal Roofing Manufacturers Inc., its directors, officers or employees shall not be responsible for any direct, indirect or special loss or damage arising from, as a consequence of, use of or reliance upon any information contained in this Code.

New Zealand Metal Roofing Manufacturers Inc. expressly disclaims any liability which is based on or arises out of the information or any errors, omissions or misstatements.

If reprinted, reproduced or used in any form, the New Zealand Metal Roofing Manufacturers Inc. (NZMRM) should be acknowledged as the source of information.

You should always refer to the current online Code of Practicefor the most recent updates on information contained in this Code.

Scope

This Code of Practice provides requirements, information and guidelines, to the Building Consent Authorities, the Building Certifier, Specifier, Designer, Licensed Building Practitioner, Trade Trainee, Installer and the end user on the design, installation, performance, and transportation of all metal roof and wall cladding used in New Zealand.

The calculations and the details contained in this Code of Practice provide a means of complying with the performance provisions of the NZBC and the requirements of the Health and Safety at Work Act 2015.

The scope of this document includes all buildings covered by NZS 3604, AS/NZS 1170 and those designed and built under specific engineering design.

It has been written and compiled from proven performance and cites a standard of acceptable practice agreed between manufacturers and roofing contractors.

The drawings and requirements contained in this Code illustrate acceptable trade practice, but recommended or better trade practice is also quoted as being a preferred alternative.

Because the environment and wind categories vary throughout New Zealand, acceptable trade practice must be altered accordingly; in severe environments and high wind design load categories, the requirements of the NZBC will only be met by using specific detailing as described in this Code.

The purpose of this Code of Practice is to present both Acceptable Trade Practice and Recommended Trade Practice, in a user-friendly format to ensure that the roof and wall cladding, flashings, drainage accessories, and fastenings will:

  • comply with the requirements of B1, B2, E1 E2 and E3 of the NZBC;
  • comply with the design loading requirements of AS/NZS 1170 and NZS 3604 and with AS/NZS 1562;
  • have and optimised lifespan; and
  • be weathertight.

COP v24.09:Revision-History; V2312-December-2023

19.4 v23.12 December 2023 

NZ Metal Roof and Wall Cladding Code of Practice v23.12

The following revisions to the NZ Metal Roof and Wall Cladding Code of Practice were published on 1 December 2023.

Substantial change to recommendations:

  • 15.1 Curved Roofs and all its sub-clauses have been substantially reviewed and revised.
  • 8.4 Flashing Cover:
    • Added clarification of rib cover to Apron Flashing Cover — Trapezoidal.
    • Changed rib height for minimum flashing cover from 25 mm to 20 mm.
    • Changed recommendation for longitudinal flashings to include both apron and barge flashings.
    • Added Category D for SED in Wind Zones up to 68 m/s.

Notable Editing and rearrangement:

The rest of the updates consisted of some renamed clauses, and minor corrections and edits.

19.4A Revision Detail v23.12 - 2023 - December

CategoryClause Number (prior to update)Clause (As of current publication)Details
2 - Editing and rearrangement3.9.33.10.2 Maximum Spans and Fastening Pattern for Corrugate Wall CladdingThis clause has been renamed and moved to 3.10 Fastening Pattern Tables – Designs to NZS 3604.
1 - Minor Errata3.10.13.10.1 G550 Steel Roof Fastening Pattern TablesClause has been renamed to clearly differentiate between roof and wall cladding fastening patterns.
3 - Substantial change to recommendation15.115.1 Curved RoofsThe main clause 15.1 Curved roof has been comprehensively reviewed and revised.
3 - Substantial change to recommendation15.1.115.1.7 Spring CurvingThis clause has been substantially revised during the overall review of 15.1 Curved Roofs.
0 - Clause Removed15.1.3Transverse LapsThis clause has been removed during the revision of 15.1 Curved Roofs. Information previously contained in this clause is now available in other sub-clauses of the main clause (15.1 Curved Roofs).
4 - Clause Inserted 15.1.3 Penetrations: Curved RoofsA newly created clause as part of the overall revision of 15.1 Curved Roofs
4 - Clause Inserted 15.1.4 Ventilation: Curved RoofsA newly created clause as part of the overall revision of 15.1 Curved Roofs.
2 - Editing and rearrangement99 External Moisture PenetrationsNew referral to RANZ Roofing Guide for further information.
4 - Clause Inserted 15.1.5 Thermal Expansion: Curved RoofsA newly created clause as part of the overall revision of 15.1 Curved Roofs.
4 - Clause Inserted 15.1.9 Installation: Curved RoofsNew clause, created from information previously contained in 15.1.11 Crimp Curving.
0 - Clause Removed15.1.6Concave RoofsThis clause has been removed during the revision of 15.1 Curved Roofs.
0 - Clause Removed15.1.10Timber FixingThis clause has been removed during the revision of 15.1 Curved Roofs.
2 - Editing and rearrangement15.1.415.1.6 DurabilityThis clause has been edited during the overall revision of 15.1 Curved Roofs.
0 - Clause Removed15.1.5Purlin SpacingThis clause has been removed during the overall revision of 15.1 Curved Roofs. The information can now be found in 15.1.7 Spring Curving.
2 - Editing and rearrangement15.1.715.1.8 Pre-Curved RoofsThis clause has been revised as part of the overall revision of 15.1 Curved Roofs.
2 - Editing and rearrangement15.1.915.1.11 Crimp Curving

This clause has been substantially edited during the revision of 15.1 Curved Roofs.

2 - Editing and rearrangement15.1.815.1.10 Roll CurvingThis clause has been revised during the overall revision of 15.1 Curved Roofs.
4 - Clause Inserted 15.1.2 End Laps: Curved RoofsNewly created clause as part of the overall revision of 15.1 Curved Roofs.
2 - Editing and rearrangement9.49.4 Penetration DesignNew referral to RANZ Roofing Guide for further information.
2 - Editing and rearrangement5.4.75.4.7 Gutter Capacity CalculatorAdditional label to clarify that gutter dimensions at the outlet are to be used for the calculation.
2 - Editing and rearrangement88 External Moisture FlashingsNew referral to RANZ Roofing Guide for further information.
2 - Editing and rearrangement8.28.2 Flashing DesignNew referral to RANZ Roofing Guide for further information.
2 - Editing and rearrangement1, 11 IntroductionUpdated Revisions Message
3 - Substantial change to recommendation15.1.215.1.1 Side Laps: Curved RoofsThis clause has been comprehensively revised during the overall review of 15.1 Curved Roofs
4 - Clause Inserted 19.4 v23.12 December 2023Revision details for V23.12; published on 1 December 2023.
2 - Editing and rearrangement8.5.2.18.5.3.1 Ridge – barge IntersectionsNew illustration showing a head barge/ridge/barge junction.
3 - Substantial change to recommendation8.48.4 Flashing Cover
  • Added clarification of rib cover to 8.4K Apron Flashing Cover — Trapezoidal.
  • Changed rib height for minimum flashing cover from 25 mm to 20 mm.
  • Changed recommendation for longitudinal flashings to include both apron and barge flashings.
  • Added Category "D" for SED up to 68 m/s, all pitches, and updated tables and the illustrations to match.  
4 - Clause Inserted 8.5.2 Head Barge/Ridge/Barge JunctionNew iIllustration of Head Barge/Ridge/Barge Junction.
2 - Editing and rearrangement8.4.18.4.1 Apron UpstandsInserted an illustration to show Undertray for additional upstand.
2 - Editing and rearrangement14.3.214.3.2 Wet Storage DamageAdded description and recommendation for dealing with Blooming.
1 - Minor Errata14.13.214.13.2 ScrewsFixed table: Screw Thread Types.
0 - Clause Removed16.2.1InstallationClause removed because the subject is comprehensively covered in Installation.
2 - Editing and rearrangement15.4.315.4.3 Tray Roofing DesignThis clause has been renamed Tray Roofing Design. Some content editing for clarity.
2 - Editing and rearrangement15.4.12.115.4.13.1 Tray Cladding Set OutThe clause has been renamed Tray Cladding Set Out and a grammar fix.
4 - Clause Inserted10.1.410.1.4 ComplianceNew Clause under 10.1 NZBC Clause E3: Internal Moisture (Extract).
2 - Editing and rearrangement15.4.615.4.7 SarkingChanged recommendation for overhang at the gutter line.
2 - Editing and rearrangement15.4.415.4.5 Tray FixingsContent editing for clarity.
2 - Editing and rearrangement15.4.215.4.2 Tray Roofing ProfilesThis clause has been renamed Tray Roofing Profiles. Some content editing.
2 - Editing and rearrangement15.4.115.4.1 Tray Roofing MaterialsRenamed the clause to Tray Roofing Materials. Some minor edits.
3 - Substantial change to recommendation15.415.4 Tray RoofingThis clause has been revised to clarify the difference between Tray roofing and standing seam roofing, as terms are used in the Code of Practice.
2 - Editing and rearrangement9.4.2.69.4.2.6 Penetration Flashings on Trapezoidal ProfilesRenamed clause to Penetration Flashings on Trapezoidal Profiles.
4 - Clause Inserted 15.4.4 Tray Roofing WeathertightnessA new clause dealing with Weathertightness and tray roofing.
4 - Clause Inserted 4.17 Tray Roofing Clip DurabilityA new clause about the durability of roofing clips.
2 - Editing and rearrangement9.4.19.4.1 Penetration Back FlashingsClause renamed to Penetration Back Flashings.
2 - Editing and rearrangement9.4.2.59.4.2.5 Penetration Flashings on Corrugated ProfilesRenamed the clause to Penetration Flashings on Corrugated Profiles.
1 - Minor Errata4, 44 DurabilityInserted a link to the 4.9.4A Interactive Material Compatibility Tool.
1 - Minor Errata14.20.214.20.2 Recommendations for Fixing AluminiumAdded "non-compressible" to point d.
1 - Minor Errata15.4.8.115.4.9.1 Tray Roofing Wind NoiseGrammar fix.
1 - Minor Errata3.4.63.4.6 Material ThicknessPunctuation fix.
1 - Minor Errata3.4.13.4.1 Corrugate ProfileGrammar fix.
1 - Minor Errata3.43.4 ProfilesTypo fix.
1 - Minor Errata33 StructurePunctuation fix.